Water is a molecule composed of two hydrogen atoms and one oxygen atom. Due to its unique physical and chemical properties, it has a tremendous ability to dissipate materials into their constituent molecules and elements, which makes pure water almost non-existent in nature. What generally is called water is actually an accumulation of dissolved elements in water. Elements in water can occur in their organic or inorganic form, and are mostly combined in molecules.
The elemental content of water typically mirrors its natural environmental exposure, e.g., its mineral content reflects the geochemical environment through which water runs (Henshaw et al., 1989; Fernandez-Turiel et al., 2000). Aqueous solutions employ water as a medium, and as such, in the case of, say, beverages, the elemental content will additionally include the effects of manufacturing processes. Aqueous biofluids primarily reflect biological functions and environmental exposure. Some aqueous solutions, such as commercial milk, will include elemental signature that reflect beverage manufacturing as well as those of biofluids. In all, aqueous solutions are expected to “fingerprint” their origin.
In theory, each naturally occurring element can be dissolved in water, and each element of the complete inorganic mass range from 6Li to 238U can be found in water, but in practice there is no comprehensive method for measuring their concentrations.
There are several techniques and methods to detect and quantify elements in fluids, and water in particular, such as high pressure liquid chromatography (“HPLC”), inductively coupled plasma atomic emission spectrometry (“IPC-AES”), inductively coupled plasma optical emission spectrometry (“ICP-OES”), and most prominently inductively coupled plasma mass spectrometry (“ICP-MS”) (Kubová et al., 1994; Rahil-Khazen et al., 2000; Leonhard et al., 2002; Taylor et al., 2003; Gonzálvez et al., 2008; Krachler and Shotyk, 2009; Ding et al., 2012; Pröfrock and Prange, 2012; Khan et al., 2013; Loop et al., 2013; Yeghicheyan et al., 2013; Jabłońska-Czapla et al., 2014; and Šelih et al., 2014).
For almost three decades, ICP-MS has been used to detect and quantify elements in various fluid samples ranging from water to breast milk, wine and body fluids (Henshaw et al., 1989; Ding et al., 2012; Krachler and Shotyk, 2009; Ammann, 2002; Ardelt et al. 2013; D'Ilio et al., 2006; De Boer et al., 1996; Forrer et al, 2001; Goullé et al., 2005; Heitland et al., 2006; Kantipuly et al., 1988; Long et al., 1989; Lyon et al., 1988; Mohd-Taufek et al. 2016; Staff et al., 2014; Stetzenbach et al., 1994; Zhang et al., 2012). Hence, ICP-MS is the technique issued by national and international guidelines to monitor water quality (Krachler and Shotyk, 2009; Heitland et al., 2006; Long et al., 1989; Louie et al., 2012; and WHO, 2011).
Although each ICP-MS has the theoretical potential for detecting each element, investigators have not done so. Until recently, all ICP-MS instruments have been so-called “sequential” ICP-MS (se-ICP-MS), in which elements are analyzed consecutively, one by one. However, a constraint over the employ of se-ICP-MS is that sample volumes must be relatively high to dispense to the instrument whilst measuring one element after the other, and significant time and consumables are required to operate these instruments; this makes it impractical to evaluate the entire relevant inorganic spectrum with se-ICP-MS.
Nevertheless, for some years se-ICP-MS has been successfully used to determine abundances and concentrations of some multiple number of elements, mostly trace elements or rear earth elements (REE), in various water samples (Henshaw et al., 1989; Stezenbach et al., 1994; DeBoer et al., 1996; Leonhard et al., 2002; Krachler and Shotyk, 2009; Louie et al., 2012), wine (Taylor et al., 2003; Gonzálvez et al., 2008; Šelih et al., 2014; and Khan et al., 2014), milk and formula (Khan et al., 2013; Khan et al., 2014), saliva, blood and urine (Lyon et al., 1988; Forrer et al., 2001; Staff et al., 2014: Koh et al., 2003; Goullé et al., 2005; Barbosa et al., 2006; D'Ilio et al., 2006; Heitland and Köster, 2006; Nriagu et al., 2006; Ding et al., 2012; and Zhang et al., 2012), liquefied tomatoes (Bressy et al., 2013) as well as in sediments and rocks (Garbe-Schönberg, 1993; Loop et al., 2013). However, because of the aforementioned constraints, se-ICP-MS studies rarely exceed 30 elements.
Recently developed “simultaneous” ICP-MS (si-ICP-MS) permits multiple elements to be detected in one evaluation from small sample volumes in seconds and at relatively low consumables and personnel costs. In 2013, the SPECTRO SI-ICP-MS (SPECTRO Analytical Instruments GmbH, Kleve, Germany) was introduced (Ardelt et al., 1998) having 4,800 detector elements, which is large enough to simultaneously detect isotope signals over the full relevant inorganic mass spectrum from 6Li to 238U (technical specifications can be found in Ardelt et al., 2013). With this technology it is possible to quantify the relatively complete elemental composition of an aqueous sample with as little as 1 mL per fluid sample. However, while the technology is able, no method has to date been developed to evaluate the complete spectrum simultaneously. An si-ICP-MS calibration method is needed for the simultaneous measurement from 6Li to 238U.
The urgent need for such a comprehensive method, especially for water, is justified by the lack of even basic data regarding element abundances and concentrations for most elements across the breadth of the inorganic spectrum (Fernandez-Turiel et al., 2000; Heitland and Köster, 2006; PAPERS describing this lack). For example, the European Union (EU) and the United States Environmental Protection Agency (EPA) are monitoring and have issued maximum concentration limits for a number of elements in drinking water considered to be health risks (EU Directive, C., 1998; EU Regulations; US EPA, 2012), yet many elements commonly known as harmful to human health, such as lithium or tin, are neither monitored nor regulated in drinking water.
The present invention is directed to overcoming these and other deficiencies in the art.